This responsive, lightweight trainer is designed for one thinggoing fast! The syncroFuel provides mild pronation control and excellent cushioning for the runner training for their next race. Seamless Race Upper with hybrid mesh combination: recycled mid foot mesh and breathable forefoot meshHalf length medial side syncro Stability FrameNEW 1:1 Energy Foam cushions the foot upon impact and then returns energy back to the runner. SKYDEXR heel crash pad.